Straw, especially rice straw, has a thick epidermis containing cutin, suberin, wax and woody tissues (lignin) bearing a small amount of silicon as well as phenolic compounds. When incinerated the ash which contains the silicon and tar particles in the smoke may drift for miles on air currents carrying the smoke. The microscopic filaments of silicon and tar particles carried in the above manner are though to be responsible for an increase in the incidence of lung cancer known to occur above normal in rice and sugar cane growing districts, where the crop residues are incinerated. For this reason alone incineration of plant residues should be discontinued. There are other reasons, however, one being the loss of valuable organic matter and plant foods from our soils. A discussion of this latter subject may be found in any text on soil science. (Buckman, H. O. and N. C. Brady, The Nature and Properties of Soils, 1960, MacMillan, N.Y.).
This application for U.S. Patent teaches that if the straw be broken or U.S. Pat. No. 4,539,799 (Kalverkamp) describes an attachment for a combine harvester leaving the discarded crop residue in minced, shredded or in small pieces on the land which may then be easily prepared for a following crop.
The Kalverkamp patent relates to our application in that it provides for breaking and shredding the crop residue so that it may be easily worked back into the soil. It makes no provision for accelerating the decomposition of the residue which, in the case of a large yield of straw, remains undecayed on the land interfering with the following crop which only invites incineration resulting in air pollution and loss of plant foods and essential humus.
U.S. Pat. Nos. 4,864,807 (Ostrup, et al.) and 4,002,010 (DaSilva Passos) also relate to our application only insofar as they, among many others, chop the harvested crop into pieces before returning it to the land. No mention is made of treating the pieces of the crop being returned to the land with a microbial nutrient enrichment for the purpose of acceleration the degradation of the crop residue to avoid its incineration, pollution of the atmosphere, conserving plant foods and humus.
U.S. Pat. No. 4,662,163 (Adams) discloses a "Mobile Spray Applicator and Method of Spraying Forage" to assist in drying, preservation and rendering the forage more palatable for animal feed, an objective directly opposite to our application. However, if the Adams machine were fitted with a device for crushing and shredding straw and applying a microbial nutrient enrichment it could be used for our purpose but would not be as efficient as similar equipment attached to the rear of a combine grain harvester.
U.S. Pat. No. 4,643,899 (Kerr, et al.), "Microorganisms Having Characteristics of an Arthrobacter Capable of Degrading Peanut Hull Lignin" discloses a group of bacteria, indigenous in soils, that are capable of degrading lignitious materials. The major objective of the Kerr patent is to improve the use of peanut hulls for animal feed by treating the hulls with a culture of the bacterial genus Arthrobacter. Forty two strains of a similar species were isolated demonstrating the soil to be their common habitat. Of course the species Arthrobacter, including the Kerr isolate, is a neutral inhabitant of agricultural soils (page 14, lines 62-65) and may be expected to be only one of a large number of indigenous species taking part in the natural degradation of cereal straw as proposed in our application. Thus, the Kerr patent reinforces our claim that by adding specific microbial nutrients to crushed shredded cereal straw its biodegradation may be accelerated. If further proof be needed see a discussion of the bacterial genus Arthrobacter by Alexander, M., Soil Microbiology, 1977, John Wiley & Sons, N.Y., who shows this genus to play a major role in the degradation of plant materials.
U.S. Pat. No. 3,266,889 (Duncan), "Method of Extracting Metals from Sulfide Ores Using Bacteria and Accelerating Agent" in which a surfactant or wetting agent is used to accelerate the process. This patent clearly demonstrates the usefulness of certain wetting agents in combination with bacteria to bring about bacterial contact with a substrate. The close contact appears to improve chemical or enzymatic responses. Obviously selected wetting agents may prove useful in the microbial nutrient enrichment liquid described in our application.
U.S. Pat. No. 4,566,469 (Semp, et al.), "Process for Dissimilatory Denitrification of Tobacco" in which the major objective is to break down and remove nitrogen bearing compounds from smoking tobaccos. The process consists of adding one or more species of a denitrifying bacteria to tobacco in the presence of a microbial culture medium enabling the microflora to increase in numbers speeding the transformation of tobacco lead nitrogen compounds to nitrogen gas. Applying a vacuum to the system accelerates the removal of the nitrogen gas.
This patent may be remotely related to our application in that a microbial nutrient medium is added to the leaf tobaccos to accelerate transformation of protein nitrogen compounds to nitrogen gas. However, the process must be carried out under anaerobic conditions for the transformation to go to completion. Our process, being strictly aerobic, ends with the nitrogen being retained and available for the fertilization of the following crop, one of the main objectives of our application.
Finally we came upon an old U.S. Pat. No. 1,900,614, Poirot, (Mar. 7, 1933), in which is disclosed a method for adding chemicals to piles of straw while the grain is being threshed; the object being to accelerate biodegradation of the straw pile to manure through action of rain and microbial oxidation. As we have emphasized elsewhere, herein, crushing and shredding the straw is an important improvement over the old art, especially for the degradation of rice straw, one of the original objectives of our application. Another improvement over the Poirot patent, as disclosed in our application, is the treated straw is spread over the entire field such that it may be turned under without interfering with the following crop. Another improvement not mentioned by the Poirot patent is the use of wetting agents or surfactants with our liquid microbial nutrient. Still another improvement and a very important one is the presence of a humectant in our microbial liquid nutrient, molasses being such a substance. It draws moisture to itself from the surrounding air enabling opportunistic fungi to start growth in the absence of precipitation.
By combining the art of harvesting cereal grains with that of microbial degradation of plant debris as, for example, the microbial degradation of cotton gin waste, U.S. Pat. No. 4,164,405, we are able to degrade cereal crop residues on the surface of the land avoiding air pollution by incineration and conserving the contained plant foods and humic natural resources of cereal crop residues.